| 1. |
- Deng, Liang, et al.
(författare)
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Numerical study of contact conditions in press hardening for tool wear simulation
- 2017
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Ingår i: International Journal of Material Forming. - : Springer. - 1960-6206 .- 1960-6214. ; 10:5, s. 717-727
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Tidskriftsartikel (refereegranskat)abstract
- In the press hardening industry, industrial and academic efforts are being directed toward predicting tool wear to realize an economical manufacturing process. Tool wear in press hardening is a tribological response to contact conditions such as pressure and sliding motion. However, these contact conditions are difficult to measure in-situ. Furthermore, press hardening involves high temperatures, and this increases the complexity of the tribo system. The present work investigated the contact conditions of press hardening with a commercial FE code (LS-DYNA) as a base for tool wear simulation. A press hardening experiment was established in industrial environments and evaluated through FE simulations. The numerical model was set up so as to approximate the manufacturing conditions as closely as possible, and the sensitivity with respect to the friction coefficients was examined. The influence of numerical factors such as the penalty value and mesh size on the contact conditions is discussed. The implementation of a modified Archard’s wear model in the FE simulation proved the possibility of tool wear simulation in press hardening. Finally, a comparison between the tool wear simulation and the measured wear depth is presented.
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| 2. |
- Huang, L. Q., et al.
(författare)
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Application of synthetic biology to sustainable utilization of Chinese materia medica resources
- 2014
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Ingår i: Yao xue xue bao = Acta pharmaceutica Sinica. - 0513-4870. ; 49:1, s. 37-43
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Forskningsöversikt (refereegranskat)abstract
- Bioactive natural products are the material bases of Chinese materia medica resources. With successful applications of synthetic biology strategies to the researches and productions of taxol, artemisinin and tanshinone, etc, the potential ability of synthetic biology in the sustainable utilization of Chinese materia medica resources has been attracted by many researchers. This paper reviews the development of synthetic biology, the opportunities of sustainable utilization of Chinese materia medica resources, and the progress of synthetic biology applied to the researches of bioactive natural products. Furthermore, this paper also analyzes how to apply synthetic biology to sustainable utilization of Chinese materia medica resources and what the crucial factors are. Production of bioactive natural products with synthetic biology strategies will become a significant approach for the sustainable utilization of Chinese materia medica resources.
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| 3. |
- Jimenez Sanchez, Carlos, 1989, et al.
(författare)
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Non-linear inversion of Odin sub-mm observations in the lower stratosphere by neural networks
- 2023
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Ingår i: Microwave Radiometry and Remote Sensing of the Earth's Surface and Atmosphere. - 9781000943467 ; , s. 503-511
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Odin is a small satellite employing sub-mm (480-580 GHz) radiometry of atmospheric thermal emission, in a limb sounding mode, to measure global distributions of several species important for ozone chemistry in the middle atmosphere. Although the planned standard data products are based on linear retrieval algorithms, addressing the non-linear effects in some of the Odin observation bands results in an extension of the retrieval altitude range into the lower stratosphere. This paper examines the possibility of applying a technique based on multilayer perceptrons to address the non-linear effects when inverting some of the future Odin data. The study is based on inverting simulated spectra in the 544.2-545.0 GHz band to retrieve O3 profiles by the neural network technique and also by an iterative implementation of the optimal estimation method based on the Marquardt-Levenberg algorithm. First results show that the proposed technique performs in similar terms when compared with the iterative implementation of the optimal estimation method, but offers the advantage of performing the inversions more efficiently from a computational point of view.
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| 4. |
- Li, Yuyi, et al.
(författare)
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Wheel wear prediction on a high-speed train in China
- 2020
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Ingår i: Vehicle System Dynamics. - : Taylor & Francis. - 0042-3114 .- 1744-5159. ; 58:12, s. 1839-1858
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Tidskriftsartikel (refereegranskat)abstract
- The number of operating high-speed trains in China is around 2800 today and 179,200 wheels are under maintenance in one reprofiling period. To help researchers to understand the evolution of the wheel profile and improve the reprofiling strategy of the wheels, this study predicts the development of wheel profiles on a high-speed train as function of mileage and compare simulated worn wheel profiles with measured ones. The methodology includes transient multi-body dynamic simulation, wheel-rail contact calculation and wear calculation with Archard's model. Calibrated by analysing measurements of worn S1002CN profiles and performing parameters sensitivity study in the wear model, the model is then used to predict the development of a recently designed wheel profile, called S1002CN-RF. The simulation results for S1002CN and S1002CN-RF show that the predicted wheel profiles coincide with the measured ones. Wear prediction of another high-speed wheel profile (LMA) validates that the vehicle performance with respect to wear could be further improved compared to using S1002CN or S1002CN-RF. Finally, the influence of track alignment and operating speed is investigated. The wear increases with the speed increasing up to 300 km/h, but stays almost constant with a further speed increase from 300 to 400 km/h.
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| 5. |
- Luo, Cheng, et al.
(författare)
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Is COX-2 a perpetrator or a protector? Selective COX-2 inhibitors remain controversial
- 2005
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Ingår i: Acta Pharmacologica Sinica. - : Springer Science and Business Media LLC. - 1671-4083 .- 1745-7254. ; 26:8, s. 926-933
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Tidskriftsartikel (refereegranskat)abstract
- COX-2(cyclooxygenase-2) has sparked a surge in pharmaceutical interest since its discovery at the beginning of the 1990s. Several COX-2 selective inhibitors that avoid gastrointestinal side effects have been successfully launched into the market in recent years. The first selective COX-2 inhibitor, celecoxib, entered the market in December 1998 [corrected] However, there are a few organs that physiologically and functionally express COX-2, particularly the glomeruli of the kidney and the cortex of the brain. Inhibition of COX-2 expression in these organs possibly causes heart attack and stroke in long-term COX-2 inhibitor users. Recently, a USA Food and Drug Agency (FDA) advisory panel re-evaluated COX-2 inhibitors and unanimously concluded that the entire class of COX-2 inhibitors increase the risk of cardiovascular problems. Thus the use of COX-2 inhibitors is still controversial, and there is a challenge for not only pharmacologists, but also the pharmaceutical industry, to develop improved painkilling and anti-inflammatory drugs. This may involve exploring a new generation of COX-2 inhibitors with different inhibitory mechanisms through computer-aided design, screening different sources of inhibitors with lower selectivity, or seeking completely new targets. Synthetic COX-2 inhibitors have high selectivity and the advantage of irreversible inhibition, whereas naturally derived COX-2 inhibitors have lower selectivity and fewer side effects, with the medical effects in general not being as striking as those achieved using synthetic inhibitors. This review discusses the mechanism of COX-2 inhibitor therapy and a possible new way of exploration in the development of anti-inflammatory, analgetic, and antipyretic drugs.
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| 6. |
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| 7. |
- Sun, Wei, 1981-
(författare)
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A New Look into Protein C Inhibitor : Posttranslational Modifications and their Functions
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The influences of posttranslational modifications on the functions of the versatile serpin protein C inhibitor (PCI) were studied. PCI is a serine protease inhibitor that is expressed in many tissues and secreted to various fluids in human, including blood plasma, seminal plasma, and urine. PCI in blood can act both as an anticoagulant and a procoagulant and is believed to play a role in pathogen defence. PCI in reproductive tissues is believed to regulate human reproduction at several steps, including the fertilization process. Due to the broad protease specificity and the contradictory activities, the physiological role of PCI is elusive. In this work the inhibitor was purified from blood and seminal plasma by immunoaffinity chromatography. Blood-derived PCI was found to be highly heterogeneous, due to variations in posttranslational modifications. The occupancy and structures of N- and O-glycans attached to blood plasma PCI and N-glycans of seminal plasma PCI were determined by mass spectrometry. An O-glycosylation site at Thr 20 was identified in PCI derived from blood. N-glycan structures of PCI isolated from blood and seminal plasma differed markedly, demonstrating that they are expressed in a tissue-specific manner. Proteolytic processing also appeared to be tissue-specific, since N-terminally cleaved PCI was found in PCI isolated both from blood and seminal plasma, but the length of the lacking segment differed. The effects of the N-linked glycans and the N-terminus of PCI on protease inhibition were determined using enzymatic measurements with chromogenic substrates. The N-glycans and the N-terminus had different effects on the inhibition of thrombin, factor Xa and prostate specific antigen, demonstrating that posttranslational modifications of PCI affect its functional specificity. These findings enhance the understanding of the regulation of the various functions of PCI and may potentially be used for the production of specialized PCI variants for medical purposes.
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| 8. |
- Yang, Zhibing, et al.
(författare)
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Two-phase flow in rough-walled fractures: Comparison of continuum and invasion-percolation models
- 2013
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Ingår i: Water resources research. - : American Geophysical Union (AGU). - 0043-1397 .- 1944-7973. ; 49:2, s. 993-1002
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Tidskriftsartikel (refereegranskat)abstract
- We present a systematic comparison study of simulating two-phase flow (drainage) in single heterogeneous fractures by using two fundamentally different approaches, namely a continuum-based two-phase flow model and an invasion percolation (IP) model. We analyze both gravity neutral and gravity destabilized cases. In the continuum model, the two-phase mass conservation equations for the two-dimensional fracture plane are solved, based on a modified TOUGH2 model. A specific capillary pressure-liquid saturation function is used to account for the sudden drainage of a local aperture location in the fracture once its local aperture-dependent non-wetting phase fluid entry pressure is exceeded. Results from the continuum model are compared to those from an invasion percolation model that includes trapping. We consider cases where the contribution of aperture-induced curvature in the capillary pressure term dominates over that of the in-plane curvature. The comparison shows that the presented continuum model can well reproduce the IP model results at low-capillary number conditions and, furthermore, can also produce meaningful results in the high capillary number regimes where IP models are not valid. Taking into account the viscous forces in the fluid displacement process, the continuum model is used to examine the effect of capillary number (reflecting the injection rate) on the phase invasion. When the injection rate varies from low to high, simulations using the continuum model show that the invasion pattern changes from single dominant fingers to more homogeneous spreading and/or clusters with numerous tortuous fingers. This trend is comparable to results from previous experimental observations in the literature. The continuum model is also used to numerically construct the upscaled (fracture-scale) capillary pressure-saturation relationship. The upscaled relationship can be well fitted to the van Genuchten and the Brook-Corey porous-medium-type models. Fracture capillary behavior depends on the aperture field heterogeneity. Simulation results indicate that increasing the aperture standard deviation leads to smaller entry pressure and larger residual water saturation.
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| 9. |
- Zhao, Anan, et al.
(författare)
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Effect of temperature on the interaction between Phlebiopsis gigantea and the root-rot forest pathogen Heterobasidion spp.
- 2015
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 340, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- The biocontrol agent Phlebiopsis gigantea is widely applied to stump surfaces during commercial thinning operations in Northern Europe to prevent airborne infection of Norway spruce (Picea abies) stumps by the root and butt-rot pathogen Heterobasidion spp. It has been suggested that warmer climatic conditions in the future may affect the interaction between the pathogen and the biocontrol agent, and may enable Heterobasidion annosum sensu stricto, which is currently restricted to southern areas of Sweden, to move further northward. To determine whether warm temperatures do effect the interaction between P. gigantea and Heterobasidion spp., we conducted a series of experiments to investigate the effect of temperature on the growth of P. gigantea and several Heterobasidion spp. and on the ability of P. gigantea to overgrow Heterobasidion spp. in paired interaction experiments in vitro. To validate our in vitro findings, we set up field experiments to examine the interaction between P. gigantea and the Heterobasidion spp. that infect spruce in Sweden, Heterobasidion parviporum and H. annosum s.s., under different temperature regimes. Our study showed that temperature did not diminish the effectiveness of P. gigantea to protect spruce stumps against infection by H. parviporum. The growth rate of P. gigantea in stumps was higher than that of H. parviporum, particularly in sapwood. We found little support for a hypothetical increase in H. annosum s.s. damage under warmer climatic conditions. In vitro studies showed that regardless of the temperature regime, H. annosum s.s. was less resistant to overgrowth by P. gigantea than H. parviporum. Under field conditions, the relatively low infection capacity of H. annosum s.s. to P. abies stumps seems to be the crucial factor determining the outcome of the interaction. The results of paired in vitro experiments between P. gigantea and non-European Heterobasidion species, for example, Heterobasidion araucariae, Heterobasidion irregulare and others, suggest that P. gigantea may be less effective as a biocontrol agent against species or isolates adapted to high temperatures (20-25 degrees C), particularly those species that are able to grow rapidly at temperatures as high as 25 degrees C. (C) 2014 Elsevier B.V. All rights reserved.
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| 10. |
- Zhu, Huaitao, et al.
(författare)
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EFFECTS OF INTERNAL COOLANT CROSSFLOW ON FILM-COOLING PERFORMANCE OF DOUBLE-JET AND CYLINDRICAL HOLES
- 2022
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Ingår i: Heat Transfer - Combustors; Film Cooling. - 9780791886038 ; 6-A
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Konferensbidrag (refereegranskat)abstract
- In this paper, the effects of internal coolant crossflow on double-jet holes were simulated and compared with two rows of cylindrical holes under three blowing ratios (M = 0.5, 1.0, and 1.5), with an established and validated turbulence model. The results show that double-jet holes can provide better film cooling performance for the three different blowing ratios compared with cylindrical holes. As the blowing ratio increases, the superiority of double-jet holes becomes more obvious. The introduction of crossflow can significantly enlarge the coolant coverage area of cylindrical holes, and increase the laterally-averaged film cooling effectiveness. For double-jet holes, the internal coolant crossflow also increases the laterally averaged film cooling effectiveness, but the improvement is limited. For the -45o compound angle film hole of double-jet holes, the internal coolant crossflow decreases the normal velocity (momentum), and makes the coolant to attach on the plate. However, for the other hole, the influence is opposite, the normal velocity (momentum) is increased and the coolant is detached from the plate.
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